Variação morfométrica entre os sexos, variabilidade genética e inferência de expansão histórica de Pygoscelis antarcticus, nas ilhas Shetland do Sul, Antártica

Abstract

Chinstrap penguin (Pygoscelis antarcticus) has their populations distributed mainly in South Sandwich, South Georgia and South Shetlands Islands, and the Antarctic Peninsula. This specie presents low sexual dimorphism, monogamy and philopatric behavior. This thesis aims to: 1) to evaluate sexual dimorphism among males and females and among two breeding areas (King George and Elephant Islands) using morphological characters and to obtain a discriminant function based on the characters that best identify the sex of Chinstrap penguins; 2) to determine the spatial structuring of population genetic variation among breeding colonies at King George and Elephant Islands, using mitochondrial control region. In the assessment of sexual dimorphism using morphological characters, were found that males were 6 to 9.4% larger than females and discriminant equation formulated correctly classifies 80.6% of the birds. There was no difference in sexual dimorphism between the breeding colonies of King George and Elephant Islands. However, the discriminant function should be used with caution in different locations than are produced because penguins may be misclassified. When discriminant equations from Deception and King George Islands were tested for Elephant Island data, we obtained only 67.7% and 71% accuracy. Where there is doubt in the field, it would be interesting to apply molecular sexing technique. For genetic variability using mitochondrial control region, were found 38 haplotypes for 61 individuals analyzed, only two were shared in the colonies and all others are exclusive. FST and AMOVA values revealed that the divergence between populations is low and that most of genetic variation (98.3%) occurred within populations. This could be explained by a high gene flow among populations, but does not corroborate with the philopatric behavior of this specie. The neutrality tests and Mismatch distribution point to a neutral evolution and possibility of expansion, which occurred more 2 Mya and the last 1 Mya, the effective population size remained constant. The results show the occurrence of a population expansion from a genetically homogeneous population and maintenance of effective size in long time scale can have widely contributed to the lack of genetic structuring among the current colonies of Chinstrap penguin.